Precise Fixation of an NO Molecule inside Carbon Nanopores: A Long‐Range Electron–Nuclear Interaction

Abstract

[60]Fullerene‐based carbon nanopores were synthesized to enable the placement of two molecules of nitric oxide (NO) at an accurate distance from one another. A linear orientation of the two NO molecules inside the assembled nanopores was confirmed crystallographically. Theoretical studies suggested possible free rotation inside the carbon nanopore, while the two conformations of NO in which its long axis was oriented toward the orifice of the nanopore were predicted to be dominant. The paramagnetic shifts caused by NO showed a major contribution from the Fermi contact mechanism. The Solomon–Bloembergen theory was found to describe well the paramagnetic relaxation enhancement of a water molecule in a paired nanopore even under equilibrium as a result of fixing of the NO molecule with a distance of approximately 12 Å, thus demonstrating a long‐range bimolecular magnetic interaction.

Synthesis of Hydrogen‐Bonded Open‐[60]Fullerenol Dimers

“…In CDCl 3 , C forms H‐bonded dimers with an association constant of K a =9.63±0.72 M −1 at 300 K. Once a water molecule is entrapped inside C , additional H‐bondings are built within the nanocavity though any proton exchange reaction does not proceed on H 2 O@ C owing to an anomalous acid/base character of the entrapped water molecule [9] . In addition, by observing a competitive association behavior between H 2 O@ C and NO@ C , a long‐range electron‐nuclear spin interaction predicted by the Solomon‐Bloembergen theory [10] was demonstrated to be present for 1 H 2 O⋅⋅⋅NO through a distance of 12 Å [11] . Thus, the face‐to‐face H‐bonding mode is useful for understanding the nature of inner chemical species.…”